August 12, 2013 Nursery-Landscape Report

You have reached Jen Llewellyn for the 16th edition of the 2013  Nursery and Landscape Report, updated on Monday, August 12th.

Environment Canada is calling for sun and cloud and continued cool (low 20’s) temperatures for this week.  It’s going to get a little bit warmer each day this week and temperatures will be up in the mid-20’s for the coming weekend. This is perfect weather for revitalizing that perennial border, mulching the gardens and playing badminton!

Lobelia cardinalis

Just the other day we were hiking around a small lake in Muskoka and we saw the most beautiful stand of Cardinal flower (Lobelia cardinalis) that I have ever seen.  This photo does not do these plants justice….but the mosquitoes were so bad that I couldn’t hold still long enough to take a decent photo.  The flowers just want on and on in a sea of scarlet-red along a low-lying area.  This native perennial can be found blooming in wet areas, in sun-partial shade.

photo 2 photo 4

Have you seen white-grey, mold-like markings like these on the bark of trees this summer? I’ve always chalked this up to some species of lichen.  Lichens are actually an organism comprised of a fungus and an algae, growing together in a mutually beneficial partnership.

Lichens 3

Lichens 3 (Photo credit: Jonah Bettio)

The algae uses sunlight to make energy and the fungus absorbs water and minerals from the air and the surface of the bark.  It is important to note, lichens do NOT harm trees.  They are merely an indication that more light is falling on the bark (sometimes because the canopy is thinning… which indicates that the tree is under stress for some other reason).

As for the white, fungal ring-like markings, we consulted a plant pathologist and he believes the white markings are the growth of the fungal partner from one of our common lichen species.  It seems to be more prevalent during wet periods and then disappears again when its dry.

Have you noticed that we have a lot more lichen around  southern Ontario now than we did even 15 years ago?  Scientists believe it is because we have less air pollution and sensitive organisms like lichens are able to grow again in densely populated and developed areas like ours.  So in a sense, lichens are bio-indicators for better air quality.  A good news story for Ontario.

Plant Phenology indicators this week. 

A) North of 401 (900-1100 GDD Base 10oC):                                                                 Hibiscus syriacus (Rose of Sharon) (full bloom), Daucus carota (wild carrot, finishing bloom), Hydrangea paniculata ‘Grandiflora’ (full bloom), Sorbus aucuparia (European Mountain ash, fruit is orange), Solidago canadensis (Canada goldenrod) (early to mid bloom).

B) Niagara: (900-1100 GDD Base 10oC):
Hibiscus syriacus (Rose of Sharon) (full bloom), Daucus carota (wild carrot, finishing bloom), Hydrangea paniculata ‘Grandiflora’ (full bloom, some turning pink), Sorbus aucuparia (European Mountain ash, fruit is orange), Solidago canadensis (Canada goldenrod) (mid to full bloom).

C) London area: if you would like to report plant phenology events, please contact me.

D) Leamington-Windsor: if you would like to report plant phenology events, please contact me.

If you are referring to the Monitoring tables in the 2009 edition of publication 383, Nursery and Landscape Plant Production and IPM, look at Tables starting on pg. 64. 

PLEASE NOTE: The Following Pesticide Recommendations are meant for Exception Uses (e.g. agriculture) under the Cosmetic Pesticide Ban unless the active ingredient is listed under Class 11 pesticides in Ontario Regulation 63/09, effective April 22, 2009.


The 2013 Crop Protection Guide for Nursery and Landscape Plants   (previously 383, now publication 840) can now be found at:

It contains the crop pest recommendations for nursery and landscape plants that was previously found in publication 383.  Publication 840 is a .pdf file, accessible online and on cd.

YelHeadSprSawflyCloseCheung Nursery-Landscape Insect Pest ID: Dave Cheung’s Common Pests of Nursery-Landscape Plants database to help ID your problem pests.


Growers. Thursday, August 15 at J.C. Bakker & Sons Nurseries.  “Intelligent Sprayer Demo Day”.
If a new sprayer design could reduce crop protection inputs by 70 percent, would you be interested? Come and see for yourself, the “intelligent sprayer”, designed and customized for nursery production
systems,  will be demonstrated for its efficiency and efficacy on real-life commercial nursery crops. Dr. Heping Zhu, well known for his extension work at Ohio State University and associate Randy Zondag will be sharing their latest research with us in St. Catharine’s.  Rain day: August 16. RSVP only. To register, click here.



Are you seeing webbing around the ends of branches on deciduous trees such as ash, birch and cherry?  Look inside the webbing and look for yellow, fuzzy caterpillars.  These are fall webworm caterpillars and they usually start to show up on the ends of branches this time of year.  Prune out nests and destroy them to prevent future colonies from infesting your trees.  Pole loppers are an awesome tool for managing fall webworm caterpillar nests!  Spraying is not necessary or necessarily effective unless there are high populations of nests.


Have white grubs been an issue in your nursery or lawn?  Applications of Beneficial nematode for white grubs (e.g. European chafer) will be effective in mid-August against early instar larvae in the soil.  Order your nematodes at least a week in advance of application.  Irrigate soil prior to application.  Never apply nematodes in direct sunlight and water well for 10-14 days after.

  DSC_0314 Japanese Beetle Feeding on Leaf

Japanese beetle adults are flying and feeding on leaves of woody plants
(Syringa, Tilia, Ulmus, Prunus, Rosa).  Look for metallic, coppery-green
beetles with white turfts of hairs along the edge of their abdomens. Adult insecticides for JB in the nursery include Sevin XLR and Imidan.  Pheromone traps for JB are extremely good at attracting the adults. Always place traps far AWAY from susceptible host trees and shrubs (e.g. roses, cherry, linden, elm, lilac etc.).

black vine weevilO_ovatusAdultDC

Black vine weevil adults and Strawberry root weevil adults are actively feeding on woody and herbaceous plants at night this time of year.  They feed by chewing out notches in leaf or needle edges.  Adult feeding is not usually detrimental to plant health but the next generation of larvae that hatch from their eggs IS damaging to plant roots.  Actara 25G, Scimitar SC, Sevin and Thionex are registered as adulticides for weevils in the nursery.



We have seen more powdery mildew on deciduous flowering shrubs (Amelanchier, Rosa) and herbaceous perennials.  Monitor for white, powdery residue on the tops and bottoms of leaves.  Protect new foliage with fungicide applications [e.g. Switch, Milstop, Regalia (biofungicide), Tivano] where the history of disease pressure is moderate to high.


Tar spot is rearing its ugly fruiting structures on Norway maple at this time.  Look for yellow halos that are filling in with black dots (those are the fruiting structures).  There is nothing you can do to prevent disease symptoms as infection took place back during leaf emergence in May.  Rake and remove newly fallen leaves or mow them to help encourage their complete breakdown before fruiting structures sporulate next spring.


Injectable insecticides may be used to protect ash trees from new infestations of Emerald Ash Borer (Agrilus planipennis).  Trees must be actively transpiring in order to maximize insecticide uptake into the cambium.   Registered injectable insecticide products include: AceCap 97, Confidor 200 SL and Tree-Azin.  Check out the Management Strategy for Emerald Ash Borer and Bronze Birch Borer at:

The regulated areas for EAB outlines restrictions on the movement of all ash species (Fraxinus sp.) materials and all species of firewood from these regulated areas of Ontario and Quebec. The regulated areas for Emerald Ash Borer in Ontario and Quebec can be found at:

Gypsy Moth Pupal Case (empty) 

FemaleGypsyMoth (Lymantria dispar)

Gypsy moth adults are emerging.  Brown males fly erratically in search of white, flightless females (photo above). Sticky bands around trunks during the flight period will trap flightless females and help prevent them from laying eggs in upper canopy.  They will also trap males to the sticky surface. Pheromone-baited sticky traps are also available to help reduce populations of adult males.

Tetranychus urticae male

Tetranychus urticae male (Photo credit: Gilles San Martin)

Two spotted spider miteTwo-spotted spider mites (TSSM) are feeding  on several types of deciduous woody (Viburnum and Spiraea in container production) and herbaceous perennials. Look for chlorotic leaves with stippling, use your hand lens to see tiny, clear bodied mites with dark regions (may be faint black) on their backs.  These mites are small but the
damage is significant so catch them early.  Miticides registered for this mite in the greenhouse include: DynoMite, Vendex, Kanemite, Floramite, Avid.  Apollo is registered in outdoor nursery crops to knock down the egg stage and newly hatched nymphs.  In the greenhouse, biocontrol agents should be brought in to coincide with the first sign of TSSM.  Phytoseiulus persimilis is a predatory mite that feeds on TSSM when temperatures are below 26oC and it is a good choice when TSSM populations are low-moderate.  Amblyseius californicus is a predatory mite that can be brought in ahead of TSSM appearance (because it can find other sources of food).  Stethorus punctillium is a new beetle that is a good predator of TSSM.


Magnolia scale apears as large, pinkish-orange scales (some may still have a dusting of white powder).  They have laid their eggs and crawlers are hatching gradually over the next 1-3 weeks (1100 + GDD Base 10C).  Pick off the scale insect and look at the underside: if it is still fleshy, they haven’t laid their eggs yet.  If tiny, white grains can be seen (like salt grains), they have started laying their eggs.  If you want to try insecticides against the crawler stage, make sure you are making at least 2-3 repeated applications, 7 days apart.  This will have much better knockdown since crawler emergence is staggered.  Insecticidal soap and the summer rate of horticultural oils should give good knock down.  Malathion, Orthene and Sevin are registered for this pest in the nursery. 


JuniperTipblight JuniperTipBlightClose

Tip dieback on Juniperus species could be the result of Juniper tip blight (Phomopsis juniperovora or Kabatina juniperi).  Look for grey, somewhat pinched, off-colour looking stem tissue just below the dead tips.  Take a closer look for black, fungal fruiting structures (photo on right).  Young, newly-emerged shoots are susceptible to infection in spring, older hardened off foliage is not.  Prune out symptomatic shoots during dry foliar conditions and DISINFECT PRUNING SHEARS with Rubbing Alcohol (isopropyl alcohol) or denatured ethanol (e.g. 70%).  Failing to disinfect pruning shears often results in spread of disease.

ThujaPestalotiopsis ThujaPestalopsisB

Tip dieback on Eastern White Cedar (Thuja occidentalis) has been pretty common this year.  We often see it during cool, wet years like this year.  Often, the weak pathogen Pestalotiopsis can be found associated with the killed tissue.  It is not a major problem and will likely be covered up by new growth in 2014.  Some light shearing will help where plants are saleable .   

Fletchers scale (3)FletcherScaleNymph

Taxus or Fletcher Scale crawlers (left) have all settled on needles and  NYMPHS are feeding on new needles (right).   These settled nymphs are much less susceptible to insecticides.  Nymphs will migrate from needles to twigs in early September, a late season insecticide rescue treatment may be possible in early September where warranted.

Euonymus Scale (tiny orange crawlers)

The second generation of Euonymus scale crawlers HAVE HATCHED.  Euonymus scale adults look like tiny white flecks (males) and brown oystershell-like (females) along twigs and the undersides of leaves.  Look for another generation of bright, orange crawlers around populations of adults and on the undersides of leaves and twigs. Where insecticide applications are warranted, multiple applications will be required to get good knockdown since crawler emergence is staggered over a few weeks.  Try insecticidal soap and the summer rate of horticultural oil.

black vine weevil RumexBVW1Monitor for black vine weevil ADULTS in the FIELD and LANDSCAPE for Rhododendron, Taxus, Thuja and Euonymus.  It’s too late for applications of nematodes in the field/landscape. Strawberry root weevil can also be a problem in field production of evergreens, adults are active.  Signs of strawberry root weevil adults include brown, flagging shoot tips (and small girdling marks at the base of the flagged shoot) on Thuja (eastern white cedar).  To scout for adult weevils, place a tarp or large piece of card board under the tree, shake branches vigorously and look for brown-black weevils “playing dead”. Insecticides for adult weevils in the nursery include Pounce, Sevin and Thiodan.  Remember, adult weevils feed at night.  Spray insecticides in late evening to target adults and reduce UV degradation (e.g. Pounce, Scimitar).



Cedar leaf miner

(CLM) next generation larvae are starting to hatch and feed on tender new foliage.  A light sheering of tips in early August should give good knockdown of CLM larvae.  Cygon is registered as a foliar application for CLM larvae in early August in the nursery.

Spruce Spider Mite

Monitor for nymphs and adults of spruce spider mite on conifers with a history of mite damage.  Spruce spider mite nymphs and adults are brown with black backs and found on new foliage this time of year.  Miticides registered for SSM include Floramite and Kanemite.  Miticides may be required where pest pressure is moderate to heavy.

THIS MESSAGE WILL BE UPDATED the week of August 26.



About Jen Llewellyn

OMAFRA Nursery and Landscape Specialist @onnurserycrops
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